5 research outputs found
A Large Underestimate of Formic Acid from Tropical Fires: Constraints from Space-Borne Measurements
Formic acid (HCOOH) is one of the
most abundant carboxylic acids
and a dominant source of atmospheric acidity. Recent work indicates
a major gap in the HCOOH budget, with atmospheric concentrations much
larger than expected from known sources. Here, we employ recent space-based
observations from the Tropospheric Emission Spectrometer with the
GEOS-Chem atmospheric model to better quantify the HCOOH source from
biomass burning, and assess whether fire emissions can help close
the large budget gap for this species. The space-based data reveal
a severe model HCOOH underestimate most prominent over tropical burning
regions, suggesting a major missing source of organic acids from fires.
We develop an approach for inferring the fractional fire contribution
to ambient HCOOH and find, based on measurements over Africa, that
pyrogenic HCOOH:CO enhancement ratios are much higher than expected
from direct emissions alone, revealing substantial secondary organic
acid production in fire plumes. Current models strongly underestimate
(by 10 ± 5 times) the total primary and secondary HCOOH source
from African fires. If a 10-fold bias were to extend to fires in other
regions, biomass burning could produce 14 Tg/a of HCOOH in the tropics
or 16 Tg/a worldwide. However, even such an increase would only represent
15–20% of the total required HCOOH source, implying the existence
of other larger missing sources
TES ammonia retrieval strategy and global observations of the spatial and seasonal variability of ammonia
Presently only limited sets of tropospheric ammonia (NH3) measurements in the Earth's atmosphere have been reported from satellite and surface station measurements, despite the well-documented negative impact of NH3 on the environment and human health. Presented here is a detailed description of the satellite retrieval strategy and analysis for the Tropospheric Emission Spectrometer (TES) using simulations and measurements. These results show that: (i) the level of detectability for a representative boundary layer TES NH3 mixing ratio value is ∼0.4 ppbv, which typically corresponds to a profile that contains a maximum level value of ∼1 ppbv; (ii) TES NH3 retrievals generally provide at most one degree of freedom for signal (DOFS), with peak sensitivity between 700 and 900 mbar; (iii) TES NH3 retrievals show significant spatial and seasonal variability of NH3 globally; (iv) initial comparisons of TES observations with GEOS-CHEM estimates show TES values being higher overall. Important differences and similarities between modeled and observed seasonal and spatial trends are noted, with discrepancies indicating areas where the timing and magnitude of modeled NH3 emissions from agricultural sources, and to lesser extent biomass burning sources, need further study. © Author(s) 2011. CC Attribution 3.0 License.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
Validation of ammonia satellite retrievals with ground-based FTIR
info:eu-repo/semantics/nonPublishe
Agricultural emissions of ammonia estimated with satellite observations and GEOS-Chem
info:eu-repo/semantics/nonPublishe